Final answer:
Reticular lichen planus is the type that typically presents on the dorsum of the tongue with a network of white lines, differing from erosive, atrophic, and bullous types. When discussing a lichen's structure, the outer layer is known as 'the cortex'.
Step-by-step explanation:
The type of lichen planus that typically presents on the dorsum of the tongue is the reticular form. This is characterized by a network of slightly raised white lines, which may look lace-like. Reticular lichen planus is generally asymptomatic and does not require treatment unless it causes discomfort. This differentiates from other forms like erosive, which is more ulcerative and symptomatic; atrophic, which involves thinning of the tissue; and bullous, which involves the formation of blisters.
When discussing the outer layer of a lichen, which is different from lichen planus affecting the tongue, the correct term is 'the cortex'. This term represents the protective layer that covers the lichen's body or thallus. Whereas the medulla is typically a layer beneath the cortex composed of loosely woven fungal hyphae.